U.S. patent number 8,803,739 [Application Number 13/038,450] was granted by the patent office on 2014-08-12 for multi-functional crlh antenna device.
This patent grant is currently assigned to Tyco Electronics Services GmbH. The grantee listed for this patent is Ajay Gummalla, Cheng Jung Lee, Vaneet Pathak, Sunil Kumar Rajgopal. Invention is credited to Ajay Gummalla, Cheng Jung Lee, Vaneet Pathak, Sunil Kumar Rajgopal.
United States Patent |
8,803,739 |
Rajgopal , et al. |
August 12, 2014 |
**Please see images for:
( Certificate of Correction ) ** |
Multi-functional CRLH antenna device
Abstract
This application relates to a multi-functional Composite Right
and Left Handed CRLH antenna device. A conductive element of a
wireless device is incorporated into the antenna structure for
reuse. In one embodiment a peripheral feature, such as a key dome,
is incorporated into the antenna device. In this way, the antenna
structure includes portions which are multi-functional.
Inventors: |
Rajgopal; Sunil Kumar (San
Diego, CA), Gummalla; Ajay (Sunnyvale, CA), Lee; Cheng
Jung (Santa Clara, CA), Pathak; Vaneet (San Diego,
CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Rajgopal; Sunil Kumar
Gummalla; Ajay
Lee; Cheng Jung
Pathak; Vaneet |
San Diego
Sunnyvale
Santa Clara
San Diego |
CA
CA
CA
CA |
US
US
US
US |
|
|
Assignee: |
Tyco Electronics Services GmbH
(CH)
|
Family
ID: |
44857839 |
Appl.
No.: |
13/038,450 |
Filed: |
March 2, 2011 |
Prior Publication Data
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Document
Identifier |
Publication Date |
|
US 20110267244 A1 |
Nov 3, 2011 |
|
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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61310220 |
Mar 3, 2010 |
|
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Current U.S.
Class: |
343/700MS;
343/720 |
Current CPC
Class: |
H01Q
1/38 (20130101); Y10T 29/49018 (20150115) |
Current International
Class: |
H01Q
1/38 (20060101); H01Q 1/24 (20060101) |
Field of
Search: |
;343/702,720,700MS |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Nguyen; Hoang V
Assistant Examiner: Holecek; Patrick
Parent Case Text
PRIORITY CLAIMS AND RELATED APPLICATIONS
This application claims the benefit of priority under 35 U.S.C.
119(e) to U.S. Provisional Patent Application Ser. No. 61/310,220,
entitled "MULTI-FUNCTIONAL COMPOSITE RIGHT AND LEFT HANDED (CRLH)
ANTENNA DEVICE," filed on Mar. 3, 2010, which is incorporated
herein by reference in its entirety.
Claims
What is claimed is:
1. A metamaterial antenna device comprising: a substrate structure;
one or more metallization layers supported by the substrate
structure and structured to include: a cell patch comprising a
first switch contact; a second switch contact configured to be
bridged to the first switch contact when a switch is actuated; a
first ground electrode formed in one of the one or more
metallization layers and conductively coupled to the cell patch
through a conductive path; and a feed structure coupled to the cell
patch; wherein the cell patch, the feed structure, and at least
part of the substrate structure are configured to form a Composite
Right/Left Handed (CRLH) antenna device structured to provide
multiple resonant operating frequencies; and wherein one or more of
the first switch contact or the second switch contact is coupled to
the first ground electrode using a frequency-selective coupling
configured to suppress a shift in the multiple resonant operating
frequencies between a state when the first and second switch
contacts are isolated from each other as compared to a state where
the first and second switch contacts are bridged.
2. The metamaterial antenna device as in claim 1, wherein the cell
patch is capacitively coupled to the feed structure.
3. The metamaterial antenna device as in claim 2, wherein the
capacitive coupling between the feed structure and the cell patch
forms a Left Hand (LH) capacitance.
4. The metamaterial antenna device as in claim 3, wherein the
conductive path is structured to provide an inductive load to the
cell patch, wherein the inductive load forms a Right Hand (RH)
inductance.
5. The metamaterial antenna device as in claim 4, wherein the RH
inductance is structured to induce a RH resonant frequency, and the
LH capacitance is structured to induce a LH resonant frequency
lower than the RH resonant frequency.
6. The device as in claim 5, wherein a RH capacitance is formed
between the cell patch and the first ground electrode, wherein the
cell patch is positioned so as to reduce the RH capacitance.
7. A method, comprising: providing a substrate structure including
one or more metallization layers; forming a cell patch comprising a
first switch contact on one of the one or more metallization
layers; forming a second switch contact on one of the one or more
metallization layers, the second switch contact configured to be
bridged to the first switch contact when a switch is actuated;
forming a first ground electrode on one of the one or more
metallization layers, the first ground electrode conductively
coupled to the cell patch through a conductive path; and forming a
feed structure on one of the one or more metallization layers, the
feed structure coupled to the cell patch; wherein the cell patch,
the feed structure, and at least part of the substrate structure
form a Composite Right/Left Handed (CRLH) antenna device structured
to provide multiple resonant operating frequencies; and wherein one
or more of the first switch contact or the second switch contact is
coupled to the first ground electrode using a frequency-selective
coupling configured to suppress a shift in the multiple resonant
operating frequencies between a state when the first and second
switch contacts are isolated from each other as compared to a state
where the first and second switch contacts are bridged.
8. The method as in claim 7, wherein the cell patch is capacitively
coupled to the feed structure.
9. The metamaterial antenna device of claim 2, wherein the feed
structure and the cell patch are located on the same metallization
layer of the substrate structure.
10. The metamaterial antenna device of claim 1, wherein the cell
patch is located on a first metallization layer of the substrate
structure; and wherein the first ground electrode is located on a
second metallization layer of the substrate structure.
11. The metamaterial antenna device of claim 10, wherein the first
ground electrode is located outside of a footprint of the cell
patch projected from the first metallization layer of the substrate
structure to the second metallization layer of the substrate
structure.
12. The metamaterial antenna device of claim 10, comprising a
second ground electrode located on the first metallization layer of
the substrate structure.
13. The metamaterial antenna device of claim 1, wherein the first
switch contact comprises an outer conductive ring; wherein the
second switch contact comprises an inner electrode located on the
same metallization layer as the outer conductive ring; and wherein
the second switch contact is located within an enclosed region
formed by the outer conductive ring of the first switch
contact.
14. The metamaterial antenna device of claim 1, comprising one or
more of an inductor or a capacitor coupled between the first switch
contact and another switch contact, the one or more of the inductor
or the capacitor configured to suppress conductive coupling of a
communication signal between the cell patch comprising the first
switch contact and another switch contact.
15. The method of claim 7, wherein the cell patch is located on a
first metallization layer of the substrate structure; wherein the
first ground electrode is located on a second metallization layer
of the substrate structure; and wherein the first ground electrode
is located outside of a footprint of the cell patch projected from
the first metallization layer of the substrate structure to the
second metallization layer of the substrate structure.
16. The metamaterial antenna device of claim 1, wherein the cell
patch comprising the first switch contact is coupled to the first
ground electrode using a frequency-selective coupling including an
inductor and a capacitor.
17. The metamaterial antenna device of claim 16, wherein one or
more of the inductor or the capacitor includes a lumped
component.
18. The metamaterial antenna device of claim 1, wherein the second
switch contact is coupled to the first ground electrode using a
frequency selective coupling including an inductor and a
capacitor.
19. The metamaterial antenna device of claim 18, wherein one or
more of the inductor or the capacitor includes a lumped
component.
20. The method of claim 7, wherein the cell patch comprising the
first switch contact is coupled to the first ground electrode using
a frequency-selective coupling including an inductor and a
capacitor.
21. The method of claim 7, if wherein the second switch contact is
coupled to the first ground electrode using a frequency selective
coupling including an inductor and a capacitor.
Description
BACKGROUND
As designers continue to add communication functionality to more
and more wireless devices, antenna circuits are developed to
communicate in a variety of scenarios. A variety of configurations
may be used to implement antennas for these multi-functional
devices.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1-3 illustrate Composite Right/Left Handed (CRLH)
Metamaterial (MTM) Transmission Line (TL) structures, according to
example embodiments;
FIGS. 4A and 4B illustrate two-port network matrix representations
for the structures of FIGS. 1-3, according to an example
embodiments;
FIG. 5 illustrates a CRLH MTM antenna structure, according to an
example embodiment;
FIGS. 6A and 6B illustrate two-port network matrix representations
for the CRLH MTM antenna structures as in FIGS. 4A and 4B,
according to example embodiments;
FIGS. 7A and 7B illustrate dispersion curves for the balanced case
and the unbalanced case, respectively, according to example
embodiments;
FIGS. 8-12 illustrate CRLH MTM TL structures with truncated ground,
according to an example embodiments;
FIG. 13 illustrates a top view of a top layer of a Printed Circuit
Board (PCB) keypad layout associated with a compact mobile device,
according to an example embodiment;
FIGS. 14A-14B illustrate a configuration of CRLH structures with
peripheral structures to form a CRLH antenna device, according to
an example embodiment;
FIGS. 15A-15C illustrate various views of a fabricated model of a
CRLH antenna device as in FIGS. 14A-14B, according to an example
embodiment;
FIGS. 16A-16B illustrate a CRLH antenna device as in FIGS. 14A-14B
with frequency-dependent isolation connectors, according to an
example embodiment;
FIGS. 17A-17C illustrate various views of a fabricated model of the
CRLH antenna device as in FIGS. 16A-16B, according to an example
embodiment;
FIG. 18 illustrates a measured return loss plot of the CRLH antenna
device without frequency-dependent connectors and CRLH antenna with
frequency-dependent connectors, according to an example
embodiment;
FIG. 19 illustrates a measured efficiency for the CRLH antenna
device without frequency-dependent connectors and CRLH antenna with
frequency-dependent connectors, according to an example
embodiment;
FIGS. 20A-20B illustrate modified implementation of the CRLH
antenna device shown in FIGS. 16A-16B, according to an example
embodiment; and
FIG. 21 illustrates a measured efficiency for the CRLH antenna
device having an antenna key in a pressed state and CRLH antenna
device having an antenna key in a released state, according to an
example embodiment.
DETAILED DESCRIPTION
The following describes a variety of configurations may be used to
implement antennas for these multi-functional devices. These
include, in some embodiments, an antenna device having a substrate
structure, such as formed on Printed Circuit Board, or other
structure having conductive layers and dielectric layers. Some
antenna devices have one or more metallization layers supported by
the substrate structure and structured to include a ground
electrode which is formed in one of the one or more metallization
layers, and a plurality of electrically conductive parts formed in
at least one of the one or more metallization layers and one or
more peripheral components, each electrically coupled to at least
one of the plurality of electrically conductive parts. The
plurality of electrically conductive parts, the one or more
peripheral components, and at least part of the substrate structure
are configured to form a CRLH antenna device.
In a variety of applications, the available space to incorporate an
antenna is limited. Some embodiments may position the antenna
structures in available space, wherein the structures have shapes
which utilize the available space. Examples of mobile devices
include a variety of electronic devices such as cell phones,
wireless laptops, and wireless USB dongles. In some of these
devices, integrated peripherals may include both conductive and
dielectric components that primarily serve a single function in the
wireless device. For example, these peripherals may include active
components such as a microphone for audio input, a speaker for
audio output, a keypad for data entry, or non-active components
such as a mechanical hinge, a fastener, or parts of an enclosure.
In some applications, the availability of these peripheral may vary
depending on the size or available features of the wireless
device.
Conventional antennas may be formed using conductive elements
associated with the peripheral components. However, these types of
antennas typically require large conductive elements and thus make
integration in compact mobile devices more challenging. Other
problems may include performance issues due unexpected radio
frequency (RF) interference caused by the peripheral component at
different operating conditions.
To address integration and antenna performance problems associated
with conventional antenna devices, antennas based on a combination
of metamaterial structures and peripheral components are
provided.
Metamaterials are manmade composite materials engineered to produce
desired electromagnetic propagation behavior not found in natural
media. The term "metamaterial" refers to many variations of these
man-made structures, including Transmission-Lines (TL) based on
CRLH propagation. A practical implementation of a pure Left-Handed
(LH) TL includes Right-Hand (RH) propagation inherited from the
lump elemental electrical parameters. This composition including LH
and RH propagation or modes, results in unprecedented improvements
in air interface integration, Over-The-Air (OTA) performance and
miniaturization while simultaneously reducing bill of materials
(BOM) costs and SAR values. MTMs enable physically small but
electrically large air interface components, with minimal coupling
among closely spaced devices. MTM antenna structures in some
embodiments are copper printed directly on the dielectric substrate
and can be fabricated using a conventional FR-4 substrate or a
Flexible Printed Circuit (FPC) board.
A metamaterial structure may be a periodic structure with N
identical unit cells cascading together where each cell is much
smaller than one wavelength at the operational frequency. A
metamaterial structure as used herein may be any RF structure to
which is applied capacitive coupling at the feed and inductive
loading to ground. In this sense, the composition of one
metamaterial unit cell is described by an equivalent lumped circuit
model having a series inductor (L.sub.R), a series capacitor
(C.sub.L), shunt inductor (L.sub.L) and shunt capacitor (C.sub.R)
where L.sub.L and C.sub.L determine the LH mode propagation
properties while L.sub.R and C.sub.R determine the RH mode
propagation properties. The behaviors of both LH and RH mode
propagation at different frequencies can be easily addressed in a
simple dispersion diagram such as described herein below with
respect to FIGS. 7A and 7B. In such a dispersion curve, .beta.>0
identifies the RH mode while .beta.<0 identifies the LH mode. An
MTM device exhibits a negative phase velocity depending on the
operating frequency.
The electrical size of a conventional transmission line is related
to its physical dimension, thus reducing device size usually means
increasing the range of operational frequencies. Conversely, the
dispersion curve of a metamaterial structure depends mainly on the
value of the four CRLH parameters, C.sub.L, L.sub.L, C.sub.R,
L.sub.R. As a result, manipulating the dispersion relations of the
CRLH parameters enables a small physical RF circuit having
electrically large RF signals. This concept has been adopted
successfully in small antenna designs.
In some applications, metamaterial (MTM) and CRLH structures and
components are based on a technology which applies the concept of
Left-handed (LH) structures. As used herein, the terms
"metamaterial," "MTM," "CRLH," "CRLH MTM," as well as "CRLH
structure," "MTM based structure," and "CRLH MTM structure," refer
to composite LH and RH structures engineered using conventional
dielectric and conductive materials to produce unique
electromagnetic properties, wherein such a composite unit cell is
much smaller than the free space wavelength of the propagating
electromagnetic waves.
Metamaterial technology, as used herein, includes technical means,
methods, devices, inventions and engineering works which allow
compact devices composed of conductive and dielectric parts and are
used to receive and transmit electromagnetic waves. Using MTM
technology, antennas and RF components may be made very compactly
in comparison to competing methods and may be very closely spaced
to each other or to other nearby components while at the same time
minimizing undesirable interference and electromagnetic coupling.
Such antennas and RF components further exhibit useful and unique
electromagnetic behavior that results from one or more of a variety
of structures to design, integrate, and optimize antennas and RF
components inside wireless communications devices
CRLH structures are structures that behave as structures exhibiting
simultaneous negative permittivity (.di-elect cons.) and negative
permeability (.mu.) in a frequency range and simultaneous positive
.di-elect cons. and positive .mu. in another frequency range.
Transmission-Line (TL) based CRLH structure are structures that
enable TL propagation and behave as structures exhibiting
simultaneous negative permittivity (.di-elect cons.) and negative
permeability (.mu.) in a frequency range and simultaneous positive
.di-elect cons. and positive .mu. in another frequency range. The
CRLH based antennas and TLs may be designed and implemented with
and without conventional RF design structures.
Antennas, RF components and other devices made of conventional
conductive and dielectric parts may be referred to as "MTM
antennas," "MTM components," and so forth, when they are designed
to behave as an MTM structure. MTM components may be easily
fabricated using conventional conductive and insulating materials
and standard manufacturing technologies including but not limited
to: printing, etching, and subtracting conductive layers on
substrates such as FR4, ceramics, LTCC, MMICC, flexible films,
plastic or even paper.
CRLH structures can be used to construct antennas, transmission
lines and other RF components and devices, allowing for a wide
range of technology advancements such as functionality
enhancements, size reduction and performance improvements. Unlike
conventional antennas, the MTM antenna resonances are affected by
the presence of the Left-Handed (LH) mode. In general, the LH mode
helps excite and better match the low frequency resonances as well
as improves the matching of high frequency resonances. These MTM
antenna structures can be fabricated by using a conventional FR-4
Printed Circuit Board (PCB) or a Flexible Printed Circuit (FPC)
board. Examples of other fabrication techniques include thin film
fabrication technique, System On Chip (SOC) technique, Low
Temperature Co-fired Ceramic (LTCC) technique, and Monolithic
Microwave Integrated Circuit (MMIC) technique.
The basic structural elements of a CRLH MTM antenna is provided in
this disclosure as a review and serve to describe fundamental
aspects of CRLH antenna structures used in a balanced MTM antenna
device. For example, the one or more antennas in the above and
other antenna devices described in this document may be in various
antenna structures, including right-handed (RH) antenna structures
and CRLH structures. In a right-handed (RH) antenna structure, the
propagation of electromagnetic waves obeys the right-hand rule for
the (E,H,.beta.) vector fields, considering the electrical field E,
the magnetic field H, and the wave vector .beta. (or propagation
constant). The phase velocity direction is the same as the
direction of the signal energy propagation (group velocity) and the
refractive index is a positive number. Such materials are referred
to as Right Handed (RH) materials. Most natural materials are RH
materials. Artificial materials can also be RH materials.
A metamaterial may be an artificial structure or, as detailed
hereinabove, an MTM component may be designed to behave as an
artificial structure. In other words, the equivalent circuit
describing the behavior and electrical composition of the component
is consistent with that of an MTM. When designed with a structural
average unit cell size .rho. much smaller than the wavelength
.lamda. of the electromagnetic energy guided by the metamaterial,
the metamaterial can behave like a homogeneous medium to the guided
electromagnetic energy. Unlike RH materials, a metamaterial can
exhibit a negative refractive index, and the phase velocity
direction may be opposite to the direction of the signal energy
propagation wherein the relative directions of the (E,H,.beta.)
vector fields follow the left-hand rule. Metamaterials having a
negative index of refraction and have simultaneous negative
permittivity .di-elect cons. and permeability .mu. are referred to
as pure Left Handed (LH) metamaterials.
Many metamaterials are mixtures of LH metamaterials and RH
materials and thus are CRLH metamaterials. A CRLH metamaterial can
behave like an LH metamaterial at low frequencies and an RH
material at high frequencies. Implementations and properties of
various CRLH metamaterials are described in, for example, Caloz and
Itoh, "Electromagnetic Metamaterials: Transmission Line Theory and
Microwave Applications," John Wiley & Sons (2006). CRLH
metamaterials and their applications in antennas are described by
Tatsuo Itoh in "Invited paper: Prospects for Metamaterials."
Electronics Letters, Vol. 40, No. 16 (August, 2004).
CRLH metamaterials may be structured and engineered to exhibit
electromagnetic properties that are tailored for specific
applications and can be used in applications where it may be
difficult, impractical or infeasible to use other materials. In
addition, CRLH metamaterials may be used to develop new
applications and to construct new devices that may not be possible
with RH materials.
Metamaterial structures may be used to construct antennas,
transmission lines and other RF components and devices, allowing
for a wide range of technology advancements such as functionality
enhancements, size reduction and performance improvements. An MTM
structure has one or more MTM unit cells. As discussed above, the
lumped circuit model equivalent circuit for an MTM unit cell
includes an RH series inductance L.sub.R, an RH shunt capacitance
C.sub.R, an LH series capacitance C.sub.L, and an LH shunt
inductance L.sub.L. The MTM-based components and devices can be
designed based on these CRLH MTM unit cells that can be implemented
by using distributed circuit elements, lumped circuit elements or a
combination of both. Unlike conventional antennas, the MTM antenna
resonances are affected by the presence of the LH mode. In general,
the LH mode helps excite and better match the low frequency
resonances as well as improves the matching of high frequency
resonances. The MTM antenna structures can be configured to support
multiple frequency bands including a "low band" and a "high band."
The low band includes at least one LH mode resonance and the high
band includes at least one RH mode resonance associated with the
antenna signal.
Some examples and implementations of MTM antenna structures are
described in the U.S. Patent Applications: Ser. No. 11/741,674
entitled "Antennas, Devices and Systems Based on Metamaterial
Structures," filed on Apr. 27, 2007; and the U.S. Pat. No.
7,592,957 entitled "Antennas Based on Metamaterial Structures,"
issued on Sep. 22, 2009. These MTM antenna structures may be
fabricated by using a conventional FR-4 Printed Circuit Board (PCB)
or a Flexible Printed Circuit (FPC) board.
One type of MTM antenna structure is a Single-Layer Metallization
(SLM) MTM antenna structure, wherein the conductive portions of the
MTM structure are positioned in a single metallization layer formed
on one side of a substrate. In this way, the CRLH components of the
antenna are printed onto one surface or layer of the substrate. For
a SLM device, the capacitively coupled portion and the inductive
load portions are both printed onto a same side of the
substrate.
A Two-Layer Metallization Via-Less (TLM-VL) MTM antenna structure
is another type of MTM antenna structure having two metallization
layers on two parallel surfaces of a substrate. A TLM-VL does not
have conductive vias connecting conductive portions of one
metallization layer to conductive portions of the other
metallization layer. The examples and implementations of the SLM
and TLM-VL MTM antenna structures are described in the U.S. patent
application Ser. No. 12/250,477 entitled "Single-Layer
Metallization and Via-Less Metamaterial Structures," filed on Oct.
13, 2008, the disclosure of which is incorporated herein by
reference.
FIG. 1 illustrates an example of a 1-dimensional (1D) CRLH MTM
transmission line (TL) based on four unit cells. One unit cell
includes a cell patch and a via, and is a building block for
constructing a desired MTM structure. The illustrated TL example
includes four unit cells formed in two conductive metallization
layers of a substrate where four conductive cell patches are formed
on the top conductive metallization layer of the substrate and the
other side of the substrate has a metallization layer as the ground
electrode. Four centered conductive vias are formed to penetrate
through the substrate to connect the four cell patches to the
ground plane, respectively. The unit cell patch on the left side is
electromagnetically coupled to a first feed line and the unit cell
patch on the right side is electromagnetically coupled to a second
feed line. In some implementations, each unit cell patch is
electromagnetically coupled to an adjacent unit cell patch without
being directly in contact with the adjacent unit cell. This
structure forms the MTM transmission line to receive an RF signal
from one feed line and to output the RF signal at the other feed
line.
FIG. 2 shows an equivalent network circuit of the 1D CRLH MTM TL in
FIG. 1. The ZLin' and ZLout' correspond to the TL input load
impedance and TL output load impedance, respectively, and are due
to the TL coupling at each end. This is an example of a printed
two-layer structure. L.sub.R is due to the cell patch and the first
feed line on the dielectric substrate, and C.sub.R is due to the
dielectric substrate being sandwiched between the cell patch and
the ground plane. C.sub.L is due to the presence of two adjacent
cell patches, and the via induces L.sub.L.
Each individual unit cell can have two resonances .omega..sub.SE
and .omega..sub.SH corresponding to the series (SE) impedance Z and
shunt (SH) admittance Y. In FIG. 2, the Z/2 block includes a series
combination of LR/2 and 2CL, and the Y block includes a parallel
combination of L.sub.L and C.sub.R. The relationships among these
parameters are expressed as follows:
.omega..times..omega..times..omega..times..times..times..omega..times..ti-
mes..times..omega..times..times..omega..times..times..times..times..times.-
.times..omega..times..times..omega..times..times..times.
##EQU00001##
The two unit cells at the input/output edges in FIG. 1 do not
include C.sub.L, since C.sub.L represents the capacitance between
two adjacent cell patches and is missing at these input/output
edges. The absence of the C.sub.L portion at the edge unit cells
prevents .omega..sub.SE frequency from resonating. Therefore, only
.omega..sub.SH appears as an m=0 resonance frequency.
To simplify the computational analysis, a portion of the ZLin' and
ZLout' series capacitor is included to compensate for the missing
C.sub.L portion, and the remaining input and output load impedances
are denoted as ZLin and ZLout, respectively, as seen in FIG. 3.
Under this condition, ideally the unit cells have identical
parameters as represented by two series Z/2 blocks and one shunt Y
block in FIG. 3, where the Z/2 block includes a series combination
of L.sub.R/2 and 2C.sub.L, and the Y block includes a parallel
combination of L.sub.L and C.sub.R.
FIG. 4A and FIG. 4B illustrate a two-port network matrix
representation for TL circuits without the load impedances as shown
in FIG. 2 and FIG. 3, respectively. The matrix coefficients
describing the input-output relationship are provided.
FIG. 5 illustrates an example of a 1D CRLH MTM antenna based on
four unit cells. Different from the 1D CRLH MTM TL in FIG. 1, the
antenna in FIG. 5 couples the unit cell on the left side to a feed
line to connect the antenna to a antenna circuit and the unit cell
on the right side is an open circuit so that the four cells
interface with the air to transmit or receive an RF signal.
FIG. 6A shows a two-port network matrix representation for the
antenna circuit in FIG. 5. FIG. 6B shows a two-port network matrix
representation for the antenna circuit in FIG. 5 with the
modification at the edges to account for the missing C.sub.L
portion to have all the unit cells identical. FIGS. 6A and 6B are
analogous to the TL circuits shown in FIGS. 4A and 4B,
respectively.
In matrix notations, FIG. 4B represents the relationship given as
below:
.times..times. ##EQU00002## where AN=DN because the CRLH MTM TL
circuit in FIG. 3 is symmetric when viewed from Vin and Vout
ends.
In FIGS. 6A and 6B, the parameters GR' and GR represent a radiation
resistance, and the parameters ZT' and ZT represent a termination
impedance. Each of ZT', ZLin' and ZLout' includes a contribution
from the additional 2C.sub.L as expressed below:
'.omega..times..times.'.omega..times..times..times.'.omega..times..times.-
.times. ##EQU00003##
Since the radiation resistance GR or GR' can be derived by either
building or simulating the antenna, it may be difficult to optimize
the antenna design. Therefore, it is preferable to adopt the TL
approach and then simulate its corresponding antennas with various
terminations ZT. The relationships in Eq. (1) are valid for the
circuit in FIG. 2 with the modified values AN', BN', and CN', which
reflect the missing C.sub.L portion at the two edges.
The frequency bands can be determined from the dispersion equation
derived by letting the N CRLH cell structure resonate with n.pi.
propagation phase length, where n=0, .+-.1, .+-.2, . . . .+-.N.
Here, each of the N CRLH cells is represented by Z and Y in Eq.
(1), which is different from the structure shown in FIG. 2, where
C.sub.L is missing from end cells. Therefore, one might expect that
the resonances associated with these two structures are different.
However, extensive calculations show that all resonances are the
same except for n=0, where both .omega..sub.SE and .omega..sub.SH
resonate in the structure in FIG. 3, and only .omega..sub.SH
resonates in the structure in FIG. 2. The positive phase offsets
(n>0) correspond to RH region resonances and the negative values
(n<0) are associated with LH region resonances.
The dispersion relation of N identical CRLH cells with the Z and Y
parameters is given below:
.times..times..beta..times..times..function..ltoreq..ltoreq..chi..ltoreq.-
.times..A-inverted..times..times..times..times..times..times..times..times-
..times..di-elect
cons..times..times..times..function..times..times..times..times..times..t-
imes..times..times..times..di-elect
cons..times..times..times..function..times. ##EQU00004## where Z
and Y are given in Eq. (1), AN is derived from the linear cascade
of N identical CRLH unit cells as in FIG. 3, and p is the cell
size. Odd n=(2 m+1) and even n=2m resonances are associated with
AN=-1 and AN=1, respectively. For AN' in FIG. 4A and FIG. 6A, the
n=0 mode resonates at .omega..sub.0=.omega..sub.SH only and not at
both .omega..sub.SE and .omega..sub.SH due to the absence of
C.sub.L at the end cells, regardless of the number of cells.
Higher-order frequencies are given by the following equations for
the different values of .chi. specified in Table 1:
.times..times..times.>.times..omega..+-..omega..omega..chi..omega..+-.-
.omega..omega..chi..omega..omega..times..omega..times.
##EQU00005##
Eq. (5)
Table 1 provides .chi. values for N=1, 2, 3, and 4. It should be
noted that the higher-order resonances |n|>0 are the same
regardless if the full C.sub.L is present at the edge cells (FIG.
3) or absent (FIG. 2). Furthermore, resonances close to n=0 have
small .chi. values (near .chi. lower bound 0), whereas higher-order
resonances tend to reach .chi. upper bound 4 as stated in Eq.
(4).
TABLE-US-00001 TABLE 1 Resonances for N= 1, 2, 3 and 4 cells
N\Modes |n| = 0 |n| = 1 |n| = 2 |n| = 3 N = 1 .chi..sub.(1, 0) = 0;
.omega..sub.0 = .omega..sub.SH N = 2 .chi..sub.(2, 0) = 0;
.omega..sub.0 = .omega..sub.SH .chi..sub.(2, 1) = 2 N = 3
.chi..sub.(3, 0) = 0; .omega..sub.0 = .omega..sub.SH .chi..sub.(3,
1) = 1 .chi..sub.(3, 2) = 3 N = 4 .chi..sub.(4, 0) = 0;
.omega..sub.0 = .omega..sub.SH .chi..sub.(4, 1) = 2 - {square root
over (2)} .chi..sub.(4, 2) = 2
The CRLH dispersion curve .beta. for a unit cell as a function of
frequency .omega. is illustrated in FIGS. 7A and 7B for the
.omega..sub.SE=.omega..sub.SH (balanced, i.e., L.sub.R
C.sub.L=L.sub.L C.sub.R) and .omega..sub.SE.noteq..omega..sub.SH
(unbalanced) cases, respectively. In the latter case, there is a
frequency gap between min(.omega..sub.SE,.omega..sub.SH) and
max(.omega..sub.SE,.omega..sub.SH). The limiting frequencies w and
.omega..sub.max values are given by the same resonance equations in
Eq. (5) with .chi. reaching its upper bound .chi.=4 as stated in
the following equations:
.omega..omega..omega..times..omega..omega..omega..times..omega..omega..ti-
mes..omega..times..times..omega..omega..omega..times..omega..omega..omega.-
.times..omega..omega..times..omega. ##EQU00006##
In addition, FIGS. 7A and 7B provide examples of the resonance
position along the dispersion curves. In the RH region (n>0) the
structure size l=Np, where p is the cell size, increases with
decreasing frequency. In contrast, in the LH region, lower
frequencies are reached with smaller values of Np, hence size
reduction. The dispersion curves provide some indication of the
bandwidth around these resonances. For instance, LH resonances have
the narrow bandwidth because the dispersion curves are almost flat.
In the RH region, the bandwidth is wider because the dispersion
curves are steeper. Thus, the first condition to obtain broadbands,
1.sup.st BB condition, can be expressed as follows:
.times..times..times..times..times..times..times..times..times..times.d.b-
eta.d.omega.dd.omega..times.<<.times..times..times..omega..omega..om-
ega..omega..+-..omega..+-..times..times.d.beta.d.omega.d.chi.d.omega..time-
s..times..chi..function..chi..times.<<.times..times..times..times..t-
imes..times..times..times..times.d.chi.d.omega..times..times..omega..+-..o-
mega..times..omega..times..omega..omega..+-. ##EQU00007## where
.chi. is given in Eq. (4) and .omega..sub.R is defined in Eq. (1).
The dispersion relation in Eq. (4) indicates that resonances occur
when |AN|=1, which leads to a zero denominator in the 1.sup.st BB
condition (COND1) of Eq. (7). As a reminder, AN is the first
transmission matrix entry of the N identical unit cells (FIG. 4B
and FIG. 6B). The calculation shows that COND1 is indeed
independent of N and given by the second equation in Eq. (7). It is
the values of the numerator and .chi. at resonances, which are
shown in Table 1, that define the slopes of the dispersion curves,
and hence possible bandwidths. Targeted structures are at most
Np=.lamda./40 in size with the bandwidth exceeding 4%. For
structures with small cell sizes p, Eq. (7) indicates that high
.omega..sub.R values satisfy COND1, i.e., low C.sub.R and L.sub.R
values, since for n<0 resonances occur at .chi. values near 4 in
Table 1, in other terms (1-.lamda./4.fwdarw.0).
As previously indicated, once the dispersion curve slopes have
steep values, then the next step is to identify suitable matching.
Ideal matching impedances have fixed values and may not require
large matching network footprints. Here, the word "matching
impedance" refers to a feed line and termination in the case of a
single side feed such as in antennas. To analyze an input/output
matching network, Zin and Zout can be computed for the TL circuit
in FIG. 4B. Since the network in FIG. 3 is symmetric, it is
straightforward to demonstrate that Zin=Zout. It can be
demonstrated that Zin is independent of N as indicated in the
equation below:
.times..times..times..times..times..chi..times. ##EQU00008## which
has only positive real values. One reason that B1/C1 is greater
than zero is due to the condition of |AN|.ltoreq.1 in Eq. (4),
which leads to the following impedance condition:
0.ltoreq.-ZY=.chi..ltoreq.4. The 2.sup.nd broadband (BB) condition
is for Zin to slightly vary with frequency near resonances in order
to maintain constant matching. Remember that the real input
impedance Zin' includes a contribution from the C.sub.L series
capacitance as stated in Eq. (3). The 2.sup.nd BB condition is
given below:
.times..times..times..times..times..times..times..times..times..times..ti-
mes..times..times..times.dd.omega..times..times..times..times.<<.tim-
es. ##EQU00009##
Different from the transmission line example in FIG. 2 and FIG. 3,
antenna designs have an open-ended side with an infinite impedance
which poorly matches the structure edge impedance. The capacitance
termination is given by the equation below:
.times. ##EQU00010## which depends on N and is purely imaginary.
Since LH resonances are typically narrower than RH resonances,
selected matching values are closer to the ones derived in the
n<0 region than the n>0 region.
One method to increase the bandwidth of LH resonances is to reduce
the shunt capacitor CR. This reduction can lead to higher
.omega..sub.R values of steeper dispersion curves as explained in
Eq. (7). There are various methods of decreasing CR, including but
not limited to: 1) increasing substrate thickness, 2) reducing the
cell patch area, 3) reducing the ground area under the top cell
patch, resulting in a "truncated ground," or combinations of the
above techniques.
The MTM TL and antenna structures in FIGS. 1 and 5 use a conductive
layer to cover the entire bottom surface of the substrate as the
full ground electrode. A truncated ground electrode that has been
patterned to expose one or more portions of the substrate surface
can be used to reduce the area of the ground electrode to less than
that of the full substrate surface. This can increase the resonant
bandwidth and tune the resonant frequency. Two examples of a
truncated ground structure are discussed with reference to FIGS. 8
and 11, where the amount of the ground electrode in the area in the
footprint of a cell patch on the ground electrode side of the
substrate has been reduced, and a remaining strip line (via line)
is used to connect the via of the cell patch to a main ground
electrode outside the footprint of the cell patch. This truncated
ground approach may be implemented in various configurations to
achieve broadband resonances.
FIG. 8 illustrates one example of a truncated ground electrode for
a four-cell MTM transmission line where the ground electrode has a
dimension that is less than the cell patch along one direction
underneath the cell patch. The ground conductive layer includes a
via line that is connected to the vias and passes through
underneath the cell patches. The via line has a width that is less
than a dimension of the cell path of each unit cell. The use of a
truncated ground may be a preferred choice over other methods in
implementations of commercial devices where the substrate thickness
cannot be increased or the cell patch area cannot be reduced
because of the associated decrease in antenna efficiencies. When
the ground is truncated, another inductor Lp (FIG. 9) is introduced
by the metallization strip (via line) that connects the vias to the
main ground as illustrated in FIG. 8. FIG. 10 shows a four-cell
antenna counterpart with the truncated ground analogous to the TL
structure in FIG. 8.
FIG. 11 illustrates another example of a MTM antenna having a
truncated ground structure. In this example, the ground conductive
layer includes via lines and a main ground that is formed outside
the footprint of the cell patches. Each via line is connected to
the main ground at a first distal end and is connected to the via
at a second distal end. The via line has a width that is less than
a dimension of the cell path of each unit cell.
The equations for the truncated ground structure can be derived. In
the truncated ground examples, the shunt capacitance C.sub.R
becomes small, and the resonances follow the same equations as in
Eqs. (1), (5) and (6) and Table 1. Two approaches are presented.
FIGS. 8 and 9 represent the first approach, Approach 1, wherein the
resonances are the same as in Eqs. (1), (5) and (6) and Table 1
after replacing L.sub.R by (LR+Lp). For |n|.noteq.0, each mode has
two resonances corresponding to (1) .omega..+-.n for L.sub.R being
replaced by (L.sub.R+Lp) and (2) .omega..+-.n for L.sub.R being
replaced by (L.sub.R+Lp/N) where N is the number of unit cells.
Under this Approach 1, the impedance equation becomes:
.times..times..times..times..times..chi..chi..times..chi..chi..chi..chi..-
times..times..times..chi..times..times..times..times..times..chi..times.
##EQU00011## where Zp=j.omega.Lp and Z, Y are defined in Eq. (2).
The impedance equation in Eq. (11) provides that the two resonances
.omega. and .omega.' have low and high impedances, respectively.
Thus, it is easy to tune near the .omega. resonance in most
cases.
The second approach, Approach 2, is illustrated in FIGS. 11 and 12
and the resonances are the same as in Eqs. (1), (5), and (6) and
Table 1 after replacing L.sub.L by (L.sub.L+Lp). In the second
approach, the combined shunt inductor (L.sub.L+Lp) increases while
the shunt capacitor C.sub.R decreases, which leads to lower LH
frequencies.
The above MTM structures are formed on two metallization layers and
one of the two metallization layers is used as the ground electrode
and is connected to the other metallization layer through a
conductive via. Such two-layer CRLH MTM TLs and antennas with a via
can be constructed with a full ground electrode as shown in FIGS. 1
and 5 or a truncated ground electrode as shown in FIGS. 8 and
10.
In one embodiment, an SLM MTM structure includes a substrate having
a first substrate surface and an opposite substrate surface, a
metallization layer formed on the first substrate surface and
patterned to have two or more conductive portions to form the SLM
MTM structure without a conductive via penetrating the dielectric
substrate. The conductive portions in the metallization layer
include a cell patch of the SLM MTM structure, a ground that is
spatially separated from the cell patch, a via line that
interconnects the ground and the cell patch, and a feed line that
is capacitively coupled to the cell patch without being directly in
contact with the cell patch. The LH series capacitance C.sub.L is
generated by the capacitive coupling through the gap between the
feed line and the cell patch. The RH series inductance L.sub.R is
mainly generated in the feed line and the cell patch. There is no
dielectric material vertically sandwiched between the two
conductive portions in this SLM MTM structure. As a result, the RH
shunt capacitance C.sub.R of the SLM MTM structure may be designed
to be negligibly small. A small RH shunt capacitance C.sub.R can
still be induced between the cell patch and the ground, both of
which are in the single metallization layer. The LH shunt
inductance L.sub.L in the SLM MTM structure is negligible due to
the absence of the via penetrating the substrate, but the via line
connected to the ground can generate inductance equivalent to the
LH shunt inductance L.sub.L. A TLM-VL MTM antenna structure may
have the feed line and the cell patch positioned in two different
layers to generate vertical capacitive coupling.
Different from the SLM and TLM-VL MTM antenna structures, a
multilayer MTM antenna structure has conductive portions in two or
more metallization layers which are connected by at least one via.
The examples and implementations of such multilayer MTM antenna
structures are described in the U.S. patent application Ser. No.
12/270,410 entitled "Metamaterial Structures with Multilayer
Metallization and Via," filed on Nov. 13, 2008, the disclosure of
which is incorporated herein by reference. These multiple
metallization layers are patterned to have multiple conductive
portions based on a substrate, a film or a plate structure where
two adjacent metallization layers are separated by an electrically
insulating material (e.g., a dielectric material). Two or more
substrates may be stacked together with or without a dielectric
spacer to provide multiple surfaces for the multiple metallization
layers to achieve certain technical features or advantages. Such
multilayer MTM structures may implement at least one conductive via
to connect one conductive portion in one metallization layer to
another conductive portion in another metallization layer. This
allows connection of one conductive portion in one metallization
layer to another conductive portion in the other metallization
layer.
An implementation of a double-layer MTM antenna structure with a
via includes a substrate having a first substrate surface and a
second substrate surface opposite to the first surface, a first
metallization layer formed on the first substrate surface, and a
second metallization layer formed on the second substrate surface,
where the two metallization layers are patterned to have two or
more conductive portions with at least one conductive via
connecting one conductive portion in the first metallization layer
to another conductive portion in the second metallization layer. A
truncated ground can be formed in the first metallization layer,
leaving part of the surface exposed. The conductive portions in the
second metallization layer can include a cell patch of the MTM
structure and a feed line, the distal end of which is located close
to and capacitively coupled to the cell patch to transmit an
antenna signal to and from the cell patch. The cell patch is formed
in parallel with at least a portion of the exposed surface. The
conductive portions in the first metallization layer include a via
line that connects the truncated ground in the first metallization
layer and the cell patch in the second metallization layer through
a via formed in the substrate. The LH series capacitance C.sub.L is
generated by the capacitive coupling through the gap between the
feed line and the cell patch. The RH series inductance L.sub.R is
mainly generated in the feed line and the cell patch. The LH shunt
inductance L.sub.L is mainly induced by the via and the via line.
The RH shunt capacitance C.sub.R is mainly induced between the cell
patch in the second metallization layer and a portion of the via
line in the footprint of the cell patch projected onto the first
metallization layer. An additional conductive line, such as a
meander line, can be attached to the feed line to induce an RH
monopole resonance to support a broadband or multiband antenna
operation.
Examples of various frequency bands that can be supported by MTM
antennas include frequency bands for cell phone and mobile device
applications, WiFi applications, WiMax applications and other
wireless communication applications. Examples of the frequency
bands for cell phone and mobile device applications are: the
cellular band (824-960 MHz) which includes two bands, CDMA (824-894
MHz) and GSM (880-960 MHz) bands; and the PCS/DCS band (1710-2170
MHz) which includes three bands, DCS (1710-1880 MHz), PCS
(1850-1990 MHz) and AWS/WCDMA (2110-2170 MHz) bands.
A CRLH structure can be specifically tailored to comply with
requirements of an application, such as PCB spatial constraints and
layout factors, device performance requirements and other
specifications. The cell patch in the CRLH structure can have a
variety of geometrical shapes and dimensions, including, for
example, rectangular, polygonal, irregular, circular, oval, or
combinations of different shapes. The via line and the feed line
can also have a variety of geometrical shapes and dimensions,
including, for example, rectangular, polygonal, irregular, zigzag,
spiral, meander or combinations of different shapes. The distal end
of the feed line can be modified to form a launch pad to modify the
capacitive coupling. Other capacitive coupling techniques may
include forming a vertical coupling gap between the cell patch and
the launch pad. The launch pad can have a variety of geometrical
shapes and dimensions, including, e.g., rectangular, polygonal,
irregular, circular, oval, or combinations of different shapes. The
gap between the launch pad and cell patch can take a variety of
forms, including, for example, straight line, curved line, L-shaped
line, zigzag line, discontinuous line, enclosing line, or
combinations of different forms. Some of the feed line, launch pad,
cell patch and via line can be formed in different layers from the
others. Some of the feed line, launch pad, cell patch and via line
can be extended from one metallization layer to a different
metallization layer. The antenna portion can be placed a few
millimeters above the main substrate. Multiple cells may be
cascaded in series to form a multi-cell 1D structure. Multiple
cells may be cascaded in orthogonal directions to form a 2D
structure. In some implementations, a single feed line may be
configured to deliver power to multiple cell patches. In other
implementations, an additional conductive line may be added to the
feed line or launch pad in which this additional conductive line
can have a variety of geometrical shapes and dimensions, including,
for example, rectangular, irregular, zigzag, planar spiral,
vertical spiral, meander, or combinations of different shapes. The
additional conductive line can be placed in the top, mid or bottom
layer, or a few millimeters above the substrate.
Another type of MTM antenna includes non-planar MTM antennas. Such
non-planar MTM antenna structures arrange one or more antenna
sections of an MTM antenna away from one or more other antenna
sections of the same MTM antenna so that the antenna sections of
the MTM antenna are spatially distributed in a non-planar
configuration to provide a compact structure adapted to fit to an
allocated space or volume of a wireless communication device, such
as a portable wireless communication device. For example, one or
more antenna sections of the MTM antenna can be located on a
dielectric substrate while placing one or more other antenna
sections of the MTM antenna on another dielectric substrate so that
the antenna sections of the MTM antenna are spatially distributed
in a non-planar configuration such as an L-shaped antenna
configuration. In various applications, antenna portions of an MTM
antenna can be arranged to accommodate various parts in parallel or
non-parallel layers in a three-dimensional (3D) substrate
structure. Such non-planar MTM antenna structures may be wrapped
inside or around a product enclosure. The antenna sections in a
non-planar MTM antenna structure can be arranged to engage to an
enclosure, housing walls, an antenna carrier, or other packaging
structures to save space. In some implementations, at least one
antenna section of the non-planar MTM antenna structure is placed
substantially parallel with and in proximity to a nearby surface of
such a packaging structure, where the antenna section can be inside
or outside of the packaging structure. In some other
implementations, the MTM antenna structure can be made conformal to
the internal wall of a housing of a product, the outer surface of
an antenna carrier or the contour of a device package. Such
non-planar MTM antenna structures can have a smaller footprint than
that of a similar MTM antenna in a planar configuration and thus
can be fit into a limited space available in a portable
communication device such as a cellular phone. In some non-planar
MTM antenna designs, a swivel mechanism or a sliding mechanism can
be incorporated so that a portion or the whole of the MTM antenna
can be folded or slid in to save space while unused. Additionally,
stacked substrates may be used with or without a dielectric spacer
to support different antenna sections of the MTM antenna and
incorporate a mechanical and electrical contact between the stacked
substrates to utilize the space above the main board.
Non-planar, 3D MTM antennas can be implemented in various
configurations. For example, the MTM cell segments described herein
may be arranged in non-planar, 3D configurations for implementing a
design having tuning elements formed near various MTM structures.
U.S. patent application Ser. No. 12/465,571 filed on May 13, 2009
and entitled "Non-Planar Metamaterial Antenna Structures", for
example, discloses 3D antennas structure that can implement tuning
elements near MTM structures. The entire disclosure of the
application Ser. No. 12/465,571 is incorporated by reference as
part of the disclosure of this document.
In one aspect, the application Ser. No. 12/465,571 discloses an
antenna device to include a device housing comprising walls forming
an enclosure and a first antenna part located inside the device
housing and positioned closer to a first wall than other walls, and
a second antenna part. The first antenna part includes one or more
first antenna components arranged in a first plane close to the
first wall. The second antenna part includes one or more second
antenna components arranged in a second plane different from the
first plane. This device includes a joint antenna part connecting
the first and second antenna parts so that the one or more first
antenna components of the first antenna section and the one or more
second antenna components of the second antenna part are
electromagnetically coupled to form a CRLH MTM antenna supporting
at least one resonance frequency in an antenna signal and having a
dimension less than one half of one wavelength of the resonance
frequency. In another aspect, the application Ser. No. 12/465,571
discloses an antenna device structured to engage a packaging
structure. This antenna device includes a first antenna section
configured to be in proximity to a first planar section of the
packaging structure and the first antenna section includes a first
planar substrate, and at least one first conductive portion
associated with the first planar substrate. A second antenna
section is provided in this device and is configured to be in
proximity to a second planar section of the packaging structure.
The second antenna section includes a second planar substrate, and
at least one second conductive portion associated with the second
planar substrate. This device also includes a joint antenna section
connecting the first and second antenna sections. The at least one
first conductive portion, the at least one second conductive
portion and the joint antenna section collectively form a CRLH MTM
structure to support at least one frequency resonance in an antenna
signal. In yet another aspect, the application Ser. No. 12/465,571
discloses an antenna device structured to engage to an packaging
structure and including a substrate having a flexible dielectric
material and two or more conductive portions associated with the
substrate to form a CRLH MTM structure configured to support at
least one frequency resonance in an antenna signal. The CRLH MTM
structure is sectioned into a first antenna section configured to
be in proximity to a first planar section of the packaging
structure, a second antenna section configured to be in proximity
to a second planar section of the packaging structure, and a third
antenna section that is formed between the first and second antenna
sections and bent near a corner formed by the first and second
planar sections of the packaging structure.
The structures described above have a variety of shapes and may be
build using one or multiple conductive layers. The structures may
also incorporate conductive material used to build or implement
other features of a device. Forming antennas from conductive
elements associated with the peripheral components may be a
challenge for conventional antenna designs in compact mobile
devices. To address integration and antenna performance problems,
typically associated with conventional antennas, antenna devices,
based on a combination of CRLH structures and peripheral components
are provided.
FIG. 13 illustrates a top view of a top layer of a printed circuit
board (PCB) keypad associated with a mobile device. The keypad
includes several alpha-numeric keys interconnected to one another
to form a 4.times.3 selectable key matrix. Each key may include a
contact switch for providing a signal to a microcontroller 1307,
depending on which key is pressed. Multiple key dome structures
1301 are formed for each key on a top and a bottom surface of a
substrate 1302. Each key dome structure 1301 includes an inner
conductive ring 1303 and an outer conductive ring 1305. Placement
of some of the key dome structures 1301 may overlap with a ground
plane 1309 while other key dome structures 1301 may overlap with an
antenna section 1313 of the substrate 1302, away from the ground
plane 1309.
FIG. 13 presents one example of a keypad configuration among
several other design possibilities. In most of these keypad
designs, however, the operation and basic structure of the keypad
typically remain the same. In one embodiment, one or more the key
dome structures 1301 in FIG. 13 may be combined with other CRLH
elements to form a CRLH antenna device as shown in FIG. 14. In FIG.
14A, for example, a CRLH antenna structure, formed in the antenna
section 1313, may include a feed line 1401 coupled to the outer
conductive ring 1305 of one of the existing key dome structures
1301. The feed line 1401 and outer conductive ring 1305 are formed
on the top surface of the substrate 1302. A via 1403 is formed in
the substrate 1302 and located near top edge portion of the outer
conductive ring 1305. FIG. 14B illustrates a top view of the bottom
surface of the substrate 1302. In FIG. 14B, the via 1403 is coupled
to a bottom ground 1407-2 through a via line 1405. The size of the
bottom ground 1407-2 may be extended by connecting it to a top
ground 1407-1 through an array of vias (not shown).
An RF source 1409 may be applied to the feed line 1401 and top
ground 1407-1 to operate the CRLH antenna device. In this example,
the LH series capacitance CL may be generated by the capacitive
coupling through the gap between the feed line 1401 and the outer
conductive ring 1305. The RH series inductance LR may be generated
in the feed line 1401 and the outer conductive ring 1305. The LH
shunt inductance LL may be induced by the via 1403 and the via line
1405. The RH shunt capacitance CR may be induced between the outer
conductive ring 1305 and a portion of the via line 1405. Notably,
the outer conductive ring 1305 may operate as a member of the key
dome structure for data input functionality and also as a cell
patch, providing the LH and RH parameters for the CRLH antenna
device. This dual-functionality design approach may offer antenna
designs that have a smaller foot print area, reduced parts and
materials, and lower fabrication costs.
FIGS. 14A-14B present one example of combining CRLH structures with
peripheral structures to form a CRLH antenna device. This design
may be beneficial in terms of reduced cost and PCB real estate.
However, antenna performance, including return loss and efficiency,
may be degraded by RF interference caused by the coupling between
the CRLH antenna device and the key dome structures. Thus,
isolating the key dome structures from the CRLH antenna may be
needed to eliminate or minimize coupling effects and improve the
performance of the antenna device.
FIGS. 15A-15C illustrates various views of a fabricated model of
the CRLH antenna device shown in FIGS. 14A-14B.
FIGS. 16A-16B illustrate an example of the CRLH antenna device
shown in FIGS. 14A-14B with frequency-dependent connectors. These
frequency-dependent connectors may provide adequate operation of
the CRLH antenna structure and the keypad during RF and DC
operation under certain conditions. Some frequency-dependent
connectors include inductors and capacitors.
According to one embodiment, a CRLH antenna structure may include a
feed line 1401 coupled to the outer conductive ring 1305 of one of
the key dome structures 1301 as shown in FIG. 16A. The feed line
1401 and outer conductive ring 1305 are formed on the top surface
of the substrate 1302. A via 1403 is formed in the substrate 1302
and located near a top edge portion of the outer conductive ring
1305.
FIG. 16B illustrates a top view of the bottom surface of the
substrate 1302. In FIG. 16B, the via 1403 is coupled to a via line
1405 that divides into two separate branches 1601 and 1603. The
first branch 1601 includes a capacitor 1605 that is coupled to the
bottom ground 1407-2 while the second branch includes an inductor
1607 that may be coupled to the outer conductive ring of another
key dome structure.
The key dome structure 1301 may also include a via 1609 formed in
the substrate and located near the center of the inner conductive
ring 1303 as shown in FIG. 16A. In FIG. 16B, for each key dome
structure 1301, the via 1609 may be connected to a corresponding
conductive line 1611 which is coupled to another inner conductive
ring 1303 of an adjacent key dome structures 1301 through an
inductor 1613.
The size of the bottom ground 1407-2 may be extended by connecting
it to a top ground 1407-1 through an array of vias (not shown).
An RF source 1409 may be applied to the feed line 1401 and top
ground 1407-1 to operate the CRLH antenna device. In operation, the
LH series capacitance CL may be generated by the capacitive
coupling through the gap between the feed line 1401 and the outer
conductive ring 1305. The RH series inductance LR may be generated
in the feed line 1401 and the outer conductive ring 1305. The LH
shunt inductance LL may be induced by the via 1403 and the via line
1405. The RH shunt capacitance CR may be induced between the outer
conductive ring 1305 and a portion of the via line 1405.
This embodiment takes into account a condition of having the key,
associated with the CRLH antenna structure, in a released state
(i.e., open switch). According to one embodiment, isolating the
ground plane 1407 from the CRLH antenna device may be accomplished
by the frequency-dependent connectors including the inductor 1613
located on each conductive line 1611, the capacitor 1605 attached
to the first via line branch, and the inductor 1607 attached to the
second via line branch. At low frequency operation, for example,
each inductor 1607 and 1613 may act as a low impedance component
which allows DC current to pass between the key dome structures
1301 in the keypad device. No current flows through the capacitor
1605 due to the high impedance the capacitor presents at the low
frequency and thus prevents the CRLH antenna from operating. While
operating at a high or microwave frequency, the inductor 1607 and
1613 may act as a high impedance component which can block current
from flowing between the key dome structures 1301 in the keypad
device and thus minimize or eliminate interference that may affect
the CRLH antenna device during high frequency operation. Operation
of the CRLH antenna device is maintained during high frequency
operation since the capacitor 1605 provides the via line 1405 a
path to the bottom ground plane 1407-2.
A number of design parameters and features of the CRLH antenna
device illustrated in FIGS. 16A-16B can be used in designing the
antenna for achieving certain antenna properties for specific
applications. Some examples are provided below.
The substrate 1302 may measure, for example, and may include
dielectric materials such as FR-4, FR-1, CEM-1 or CEM-3. These
materials may have a dielectric constant measuring approximately
4.4, for example.
In FIGS. 16A-16B, each inductor may have an inductance measuring
approximately 100 nH, and the capacitor may have a capacitance
measuring approximately 27 pF.
FIGS. 17A-17C illustrates various views of a fabricated model of
the CRLH antenna device shown in FIGS. 16A-16B.
FIG. 18 illustrates a measured return loss plot of the CRLH antenna
device without frequency-dependent connectors (dashed line) and
multi-functional CRLH antenna device with frequency-dependent
connectors (solid line). The measured return loss suggests the
multi-functional CRLH antenna with the frequency-dependent
connectors operates similar to the reference antenna (i.e., without
connectors). This result is significant since it shows that the
multi-functional CRLH antenna device operates well while the device
is actively supporting keypad functions. Thus, RF interference
produced during keypad operations, including the active DC current
flow, is minimized in the multi-functional CRLH antenna device.
FIG. 19 illustrates a measured efficiency for the CRLH antenna
device without frequency-dependent connectors (dashed line) and
multi-functional CRLH antenna with frequency-dependent connectors
(solid line). This result indicates that the device may be capable
of achieving an average efficiency, over a given range of
frequency, which is equal or better than 65%. This result provides
further support on the broad performance capability of the
multi-functional CRLH antenna device while connected to other
peripheral components.
FIGS. 20A-20B illustrate an example of the CRLH antenna device
shown in FIGS. 16A-16B with an additional capacitor connected to
the conductive line 1611. This embodiment takes into account a
condition of having the key, associated with the CRLH antenna
structure, in a pressed state (i.e., closed switch). While this key
is pressed, contact is made between the inner conductive ring 1303
and the outer conductive ring 1305, forming a larger conductive
surface area. Since a portion of the CRLH antenna device includes
the outer conductive ring 1305, pressing the key can influence the
resonance frequency or bandwidth of the antenna. To minimize the
effects of shifts in the resonance frequency or bandwidth of the
antenna, a second capacitor 2001 is connected between the
conductive line 1611 and the bottom ground 1407-2. Thus, operation
of the CRLH antenna device is maintained during high frequency
operation since the second capacitor 2001 may dominate the first
capacitor 1605 and provides a shorter path to the bottom ground
plane 1407-2.
FIG. 21 illustrates a measured efficiency for the CRLH antenna
device with the antenna key released (dashed line) and the CRLH
antenna device with the antenna key pressed (solid line). This
result indicates that the device may be capable of achieving an
average efficiency, over a given range of frequency, which is equal
or better than 50%. This result provides further support on the
broad performance capabilities of the multi-functional CRLH antenna
device while the antenna key is operating in a pressed or released
state.
In another configuration, the size, shape, connection and location
of the key dome structures may be modified to improve or enhance
the CRLH antenna device performance. Also, multiple CRLH antenna
devices, such as a CRLH WiFi antenna device and a secondary
Bluetooth antenna device, may be formed using a various combination
of available peripheral structures such as the multiple key dome
structures. In addition, the multiple key dome structures may be
combined and configured with other CRLH structures to form a dipole
antenna or balanced CRLH antenna device.
In yet another configuration, the multiple key dome structures can
be combined and configured with other CRLH structures to form an
antenna with differential input. This differential antenna can be
directly fed to a differential Low Noise Amplifier (LNA)
eliminating the need for a balun, which in turn improve noise
performance and reduces insertion loss.
Other types CRLH antenna devices may be formed using various
peripheral components available on the PCB including, for example,
a laptop keyboard, a built-in camera, a speaker, a microphone (with
EMI considerations), and an LCD/LED.
The multi-functional CRLH antenna devices presented above may be
configured to operate in various frequency bands including
multiband, single-band, and low-band.
While this specification contains many specifics, these should not
be construed as limitations on the scope of any invention or of
what may be claimed, but rather as descriptions of features
specific to particular embodiments. Certain features that are
described in this specification in the context of separate
embodiments may also be implemented in combination in a single
embodiment. Conversely, various features that are described in the
context of a single embodiment may also be implemented in multiple
embodiments separately or in any suitable subcombination. Moreover,
although features may be described above are acting in certain
combinations and even initially claimed as such, one or more
features from a claimed combination may in some cases be exercised
from the combination, and the claimed combination may be directed
to a subcombination or variation of a subcombination.
Thus, particular embodiments have been described. Variations,
enhancements and other embodiments may be made based on what is
described and illustrated.
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